There is an interesting article in the Sunday, Oct 13, 1996
edition of the Washington Post about a person picking
up every coin he found on the ground since 1985 and
entering all the details into a database! There is a graph
that show how many coins he picked up per month since 1985
(only in the hardcopy, but discussed in the article).
The oldest coin he found was an 1891 Indian Head 'penny'
(also only in the hardcopy edition). I found it entertaining,
even if he did call the San Fransico mint 'defunct'.
You can find the article, titled "Tails over Heads", on-line at: